He’s got a comfortable lead in the polls, but Mayor Bloomberg isn’t taking any chances on his bid for a third term and will launch TV campaign commercials earlier this year than he did in 2005, The Post has learned.

The mayor intends to be on the air well before May 18, which is when he started a $1 million-a-week TV blitz in his first re-election run four years ago, a source said.

Bloomberg is considering opening nearly two dozen campaign offices around the city as early as April, another source said.

No decision has been made on the timing of the TV ads, said Howard Wolfson, the mayor’s campaign spokesman. He denied that campaign offices were on the drawing boards.

A Quinnipiac University poll out yesterday pronounced Bloomberg “bulletproof” because he was maintaining a healthy 65 percent approval rating, down from 69 percent on Jan. 27. His disapproval rate is 25 percent.